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Message-ID: <878vrs2if3.fsf@rustcorp.com.au>
Date: Thu, 21 Jul 2011 17:07:36 +0930
From: Rusty Russell <rusty@...tcorp.com.au>
To: Jonathan Cameron <jic23@....ac.uk>, Tejun Heo <tj@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: RFC: Boiler plate functions for ida / idr allocation?
On Wed, 13 Jul 2011 14:48:34 +0100, Jonathan Cameron <jic23@....ac.uk> wrote:
> > Here's an interface that I think should work,
> >
> > int ida_get(struct ida *ida, int begin, int end, gfp_t gfp);
> >
> > It uses an internal spinlock, returns the allocated ID and @end <= 0
> > indicates no limit.
> Cool.
>
> Rusty, are you pursuing this? Approach looks sensible to me.
Yep, here's my latest version. Feel free to run with it, or not.
Thanks!
Rusty.
From: Rusty Russell <rusty@...tcorp.com.au>
Subject: ida: Simplified functions for id allocation.
The current hyper-optimized functions are overkill if you simply want
to allocate an id for a device. Create versions which use an internal
lock.
Thanks to Tejun for feedback. Feel free to delete the #ifdef TEST
code.
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
include/linux/idr.h | 4 +
lib/idr.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 120 insertions(+)
diff --git a/include/linux/idr.h b/include/linux/idr.h
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -146,6 +146,10 @@ void ida_remove(struct ida *ida, int id)
void ida_destroy(struct ida *ida);
void ida_init(struct ida *ida);
+int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
+ gfp_t gfp_mask);
+void ida_simple_remove(struct ida *ida, unsigned int id);
+
void __init idr_init_cache(void);
#endif /* __IDR_H__ */
diff --git a/lib/idr.c b/lib/idr.c
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -34,8 +34,10 @@
#include <linux/err.h>
#include <linux/string.h>
#include <linux/idr.h>
+#include <linux/spinlock.h>
static struct kmem_cache *idr_layer_cache;
+static DEFINE_SPINLOCK(simple_ida);
static struct idr_layer *get_from_free_list(struct idr *idp)
{
@@ -926,6 +928,120 @@ void ida_destroy(struct ida *ida)
EXPORT_SYMBOL(ida_destroy);
/**
+ * ida_simple_get - get a new id.
+ * @ida: the (initialized) ida.
+ * @start: the minimum id (inclusive, < 0x8000000)
+ * @end: the maximum id (exclusive, < 0x8000000 or 0)
+ * @gfp_mask: memory allocation flags
+ *
+ * Allocates an id in the range start <= id < end, or returns -ENOSPC.
+ * On memory allocation failure, returns -ENOMEM.
+ *
+ * Use ida_simple_remove() to get rid of an id.
+ */
+int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
+ gfp_t gfp_mask)
+{
+ int ret, id;
+ unsigned int max;
+
+ BUG_ON((int)start < 0);
+ BUG_ON((int)end < 0);
+
+ if (end == 0)
+ max = 0x80000000;
+ else {
+ BUG_ON(end < start);
+ max = end - 1;
+ }
+
+again:
+ if (!ida_pre_get(ida, gfp_mask))
+ return -ENOMEM;
+
+ spin_lock(&simple_ida);
+ ret = ida_get_new_above(ida, start, &id);
+ if (!ret) {
+ if (id > max) {
+ ida_remove(ida, id);
+ ret = -ENOSPC;
+ } else {
+ ret = id;
+ }
+ }
+ spin_unlock(&simple_ida);
+
+ if (unlikely(ret == -EAGAIN))
+ goto again;
+
+ return ret;
+}
+EXPORT_SYMBOL(ida_simple_get);
+
+/**
+ * ida_simple_remove - remove an allocated id.
+ * @ida: the (initialized) ida.
+ * @id: the id returned by ida_simple_get.
+ */
+void ida_simple_remove(struct ida *ida, unsigned int id)
+{
+ BUG_ON((int)id < 0);
+ spin_lock(&simple_ida);
+ ida_remove(ida, id);
+ spin_unlock(&simple_ida);
+}
+EXPORT_SYMBOL(ida_simple_remove);
+
+#ifdef TEST
+static int test_ida_simple(void)
+{
+ int i;
+ DEFINE_IDA(ida);
+
+ /* Simple range 0..0. */
+ i = ida_simple_get(&ida, 0, 1, GFP_KERNEL);
+ BUG_ON(i != 0);
+ i = ida_simple_get(&ida, 0, 1, GFP_KERNEL);
+ BUG_ON(i != -ENOSPC);
+ ida_simple_remove(&ida, 0);
+ i = ida_simple_get(&ida, 0, 1, GFP_KERNEL);
+ BUG_ON(i != 0);
+
+ /* Empty range. */
+ i = ida_simple_get(&ida, 0x7FFFFFFE, 0x7FFFFFFE, GFP_KERNEL);
+ BUG_ON(i != -ENOSPC);
+
+ /* Top of range. */
+ i = ida_simple_get(&ida, 0x7FFFFFFE, 0x7FFFFFFF, GFP_KERNEL);
+ BUG_ON(i != 0x7FFFFFFE);
+ i = ida_simple_get(&ida, 0x7FFFFFFE, 0x7FFFFFFF, GFP_KERNEL);
+ BUG_ON(i != -ENOSPC);
+ ida_simple_remove(&ida, 0x7FFFFFFE);
+
+ /* End of range testing. */
+ i = ida_simple_get(&ida, 0x7FFFFFFE, 0, GFP_KERNEL);
+ BUG_ON(i != 0x7FFFFFFE);
+
+ i = ida_simple_get(&ida, 0x7FFFFFFE, 0, GFP_KERNEL);
+ BUG_ON(i != 0x7FFFFFFF);
+
+ i = ida_simple_get(&ida, 0x7FFFFFFE, 0, GFP_KERNEL);
+ BUG_ON(i != -ENOSPC);
+
+ /* Remove works. */
+ i = ida_simple_get(&ida, 0x7FFFFFFD, 0, GFP_KERNEL);
+ BUG_ON(i != 0x7FFFFFFD);
+
+ ida_simple_remove(&ida, 0x7FFFFFFE);
+ i = ida_simple_get(&ida, 0x7FFFFFFD, 0, GFP_KERNEL);
+ BUG_ON(i != 0x7FFFFFFE);
+
+ ida_destroy(&ida);
+ return 0;
+}
+#endif
+
+/**
* ida_init - initialize ida handle
* @ida: ida handle
*
--
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